The Tervamäki JT-5, later marketed as the VPM MT-5, is a single-seat autogyro developed in Finland[1] by Jukka Tervamäki in the early 1970s and which was marketed in kit form for amateur construction.[2] A development of his ATE-3 design of 1968, the JT-5 first flew in 1973,[2] and Tervamäki sold the prototype, its tooling, and its manufacturing rights the following year.[3]
| JT-5 | |
|---|---|
| Role | recreational autogyro |
| National origin | Finland |
| Manufacturer | homebuilt |
| Designer | Jukka Tervamäki |
| First flight | 7 January 1973 |
| Number built | at least 5 |
| Developed from | Tervamäki ATE-3 |
| Developed into | VPM MT-7 |
Design
editThe JT-5 features a streamlined fuselage pod that fully encloses its cockpit and a single, piston engine that drives a pusher propeller.[2] It has a two-bladed main rotor, and fixed, tricycle undercarriage.[2] The structure makes extensive use of composite materials[2][3] around a frame of welded steel tube.[2][4] The empennage is a triple tail that consists of a large fin and rudder plus smaller fins at the ends of the horizontal stabiliser,[2] an arrangement that Tervamäki compared to that of the Lockheed Constellation.[5] This configuration was chosen to increase the area of the tail surfaces and therefore the static and dynamic stability of the aircraft.[5] Tervamäki saw this as an important safety feature to reduce the possibility of pilot-induced oscillation, which had been implicated in fatal autogyro crashes.[5]
The cockpit is enclosed by an expansive plexiglass canopy that hinges sideways.[2][3] The instrument panel and the firewall that separates the cockpit from the rotor mast and engine hinge together with the canopy.[2][3] This feature was intended to facilitate inspection and maintenance of the instruments, nosegear, rudder pedals, and front side of the engine.[5] The level of access to the engine that this created was so great that most routine engine inspection tasks could be carried out without removing the cowling.[6]
Provisions for cold weather include an optional cabin heater, a ventilation system to prevent canopy fogging, and a carburettor heater.[5][7]
The prototype was powered by a Volkswagen automotive engine modified for aero use by Limbach Motorenbau.[2] VPM specified a Limbach L1700 for the MT-5 instead.[8] The aircraft is equipped with a pre-rotation mechanism for the rotor.[2][4]
Development
editDesign work on the JT-5 began in 1969, and construction of the prototype the following year.[3] Initially, the work was shared between Tervamäki and Aulis Eerola, with whom he had collaborated on the ATE-3.[3] Eerola contributed to some of the construction work, but departed the project before its completion.[3] Some of the funding for the development work came from a grant by the Finnish Technical Foundation.[3][9] Tervamäki estimated that around 2,000 hours' work went into the prototype[9][10] over three years.[9] He later reflected that this level of effort was contrary to one of the main reasons he had originally been drawn to autogyros: their simplicity.[11]
The prototype first flew on 7 January 1973, carrying the registration OH-XYS.[2]
By then, however, Tervamäki's focus was on his JT-6 motorglider, and he realised that he would not have time to effectively market and support the JT-5.[9] Therefore, in 1974, he sold the prototype, together with its moulds, tooling, and manufacturing rights to Vittorio Magni.[3][9] In 1979, Magni founded the VPM company to market components and complete kits of the aircraft under the name VPM MT-5.[2] The following year, Magni contracted Tervamäki to design an enlarged, two-seat derivative, the MT-7.
In 1986, VPM sold the rights to the MT-5 and MT-7 to Spanish firm Cenemesa.[12]
Apart from the prototype, at least four other JT-5s were built by 2009, three in Finland and one in Sweden, with a number of others under construction.[3] Tervamäki continued to sell JT-5 plans for some time,[3] with around 60 sets sold by 1979.[10] He later made them available for free download on his personal website.[13]
Specifications (prototype JT-5)
editData from Taylor 1986, p.564
General characteristics
- Crew: one pilot
- Length: 3.50 m (11 ft 6 in) (fuselage)
- Empty weight: 167 kg (368 lb)
- Max takeoff weight: 290 kg (639 lb)
- Powerplant: 1 × Volkswagen four-cylinder, horizontally-opposed, air-cooled automotive engine, 56 kW (75 hp)
- Main rotor diameter: 7.00 m (23 ft 0 in)
- Main rotor area: 38.50 m2 (414.4 sq ft)
Performance
- Maximum speed: 170 km/h (110 mph, 92 kn)
- Cruise speed: 150 km/h (93 mph, 81 kn)
- Range: 350 km (220 mi, 190 nmi)
- Service ceiling: 4,000 m (13,000 ft)
- Rate of climb: 3 m/s (590 ft/min)
Notes
editReferences
edit- ^ Taylor 1993, p.855
- ^ a b c d e f g h i j k l m Taylor 1987, p.564
- ^ a b c d e f g h i j k Charnov 2009
- ^ a b Markowski 1984, p.417
- ^ a b c d e Tervamäki 1974, p.40
- ^ Tervamäki 1973, p.24
- ^ Shelbourne 1979, p.29
- ^ Taylor 1986, p.604
- ^ a b c d e Tervamäki 1974, p.41
- ^ a b Shelbourne 1979, p.28
- ^ Raivio 1973, p.12
- ^ La Storia
- ^ Tervamäki, n.d.
Bibliography
edit- Charnov, Bruce H. (27–29 May 2009). From Rolf von Bahr to Jukka Tervamäki: The Scandinavian Influence on European Gyroplane History. American Helicopter Society 65th Annual Forum. Archived from the original on 5 May 2009. Retrieved 23 July 2024.
- Raivio, Jyri (May 1973). "Tuo lentävä mies mainiossa koneessaan" [That flying man in his magnificent plane]. Ilmailu. Vol. 36, no. 5. Helsinki: Suomen ilmailuliitto. pp. 10–12.
- Shelbourne, Walter (October 1979). "The Jukka Tervamaki JT-5". Homebuilt Aircraft. Vol. 5, no. 8. pp. 28–29.
- "La Storia" [History]. Magni Gyro: produzione autogiri per il lavoro e per il tempo libero. Besante: Magni Gyro srl. Retrieved 23 July 2024.
- Markowski, Mark (1984). The Encyclopedia of Homebuilt Aircraft. Blue Ridge Summit, Pennsylvania: Tab Books.
- Taylor, John W.R., ed. (1986). Jane's All the World's Aircraft 1986-87 (77th ed.). London: Jane's Pub.
- Taylor, John W.R., ed. (1987). Jane's All the World's Aircraft 1987-88 (78th ed.). London: Jane's Information Group.
- Taylor, Michael J. H. (1993). Jane's Encyclopedia of Aviation. London: Studio Editions.
- Tervamäki, Jukka (n.d.). "The JT-5 Autogyro". The Home Page of Jukka Tervamaki. Retrieved 23 July 2024.
- Tervamäki, Jukka (August 1973). "New Super Sleek Autogyro From Finland". Popular Rotorcraft Flying. Vol. 11, no. 3. Raleigh, North Carolina: Popular Rotorcraft Association. p. 24.
- Tervamäki, Jukka (February 1974). "The Sleek New JT-5 From Finland". Sport Aviation. Vol. 23, no. 2. pp. 39–41, 61.